Interaction of Mediterranean water eddies with Sedlo and Seine Seamounts, Subtropical Northeast Atlantic

Abstract During years 2003 and 2004 both Sedlo and Seine Seamounts, lying in the area of influence of the Mediterranean water outflow in the Northeast Atlantic, were investigated in the framework of the EU-funded project OASIS. Analysis of CTD data shows that the levels of major variability in temperature and salinity were confined to the upper ocean layer, which is subject to seasonal air–sea heat exchange, and to the Mediterranean Water (MW) level. In this paper we concentrate on the latter case and show that the variability observed resulted from Mediterranean water eddies (Meddies) colliding with the seamounts. Combined data from CTD surveys, current meter moorings, ship-mounted ADCP and satellite altimetry suggest that during the period of observations there was only one Meddy interacting with each of the seamounts. On Sedlo Seamount intensive interaction resulted in the loss by the Meddy of about 25% of the salt around the seamount, whereas on Seine the Meddy (or portion of it) escaped the seamount after performing several rotations around the summit without any significant interaction.

[1]  M. Arhan,et al.  Volume budget of the eastern boundary layer off the Iberian Peninsula , 1997 .

[2]  William J. Emery,et al.  Data Analysis Methods in Physical Oceanography , 1998 .

[3]  Xavier Carton,et al.  Hydrological and dynamical characterization of Meddies in the Azores region: A paradigm for baroclinic vortex dynamics , 1998 .

[4]  Bablu Sinha,et al.  Position and structure of the Subtropical/Azores Front region from combined Lagrangian and remote sensing (IR/altimeter/SeaWiFS) measurements , 1999, Journal of the Marine Biological Association of the United Kingdom.

[5]  Rachel M. Jeffreys,et al.  Deep-Sea Research II , 2008 .

[6]  R. Pingree,et al.  Ocean structure and climate (Eastern North Atlantic): in situ measurement and remote sensing (altimeter) , 2002, Journal of the Marine Biological Association of the United Kingdom.

[7]  M. Mccartney,et al.  Spreading of Labrador Sea Water in the eastern North Atlantic , 1998 .

[8]  J. Marshall.  Submarine salt lenses , 1988, Nature.

[9]  C. Cenedese.  Laboratory experiments on mesoscale vortices colliding with a seamount , 2002 .

[10]  K. F. Bowden.  Physical oceanography of coastal waters , 1983 .

[11]  A. Verdière,et al.  Instability dynamics of a subtropical jet and applications to the azores front current system : Eddy-driven mean flow , 1999 .

[12]  Y. Morel,et al.  Interaction between an eddy and a zonal jet - Part II. Two-and-a-half-layer model , 2003 .

[13]  T. Müller,et al.  Meddies and decadal changes at the Azores Front from 1980 to 2000 , 2005 .

[14]  William J. Emery,et al.  Strong Current Events Related to a Subtropical Front in the Northeast Atlantic , 1985 .

[15]  W. J. Gould,et al.  Physical oceanography of the Azores front , 1985 .

[16]  M. Tsuchiya.  Circulation of the Antarctic Intermediate Water in the North Atlantic Ocean , 1989 .

[17]  G. Reverdin,et al.  Variability of the Azores Current during October–December 1993 , 2001 .

[18]  W. Krauss.  The Warmwatersphere of the North Atlantic Ocean , 1996 .

[19]  H. V. Aken.  The hydrography of the mid-latitude Northeast Atlantic Ocean: II: The intermediate water masses , 2000 .

[20]  M. Arhan,et al.  The Eastern Boundary of the Subtropical North Atlantic , 1994 .

[21]  A. New,et al.  On the role of the Azores Current in the ventilation of the North Atlantic Ocean , 2001 .

[22]  John M. Toole,et al.  Tidally Driven Vorticity, Diurnal Shear, and Turbulence atop Fieberling Seamount , 1997 .

[23]  G. Siedler,et al.  Seasonal changes in the North Atlantic subtropical Gyre , 1988 .

[24]  Hans-Harald Hinrichsen,et al.  Can meddies be detected by satellite altimetry , 1991 .

[25]  P. L. Traon,et al.  Large structures and temporal change in the Azores Front during the SEMAPHORE experiment , 1998 .

[26]  J. Church,et al.  Ocean Circulation and Climate: Observing and Modelling the Global Ocean , 2001 .

[27]  E. Firing,et al.  Processing ADCP data with the CODAS software system version 3.1 , 1995 .

[28]  P. Davies,et al.  A monopolar vortex encounters an isolated topographic feature on a β-plane , 2000 .

[29]  W. Zenk,et al.  The Madeira Mode Water , 1987 .

[30]  Eric Blayo,et al.  Assessment of the ocean circulation in the Azores region as predicted by a numerical model assimilating altimeter data from Topex/Poseidon and ERS-1 satellites , 1997 .

[31]  Philip L. Richardson,et al.  Two Years in the Life of a Mediterranean Salt Lens , 1989 .

[32]  G. Shapiro,et al.  Mediterranean lens irving after its collision with seamounts , 1995 .

[33]  B. Klein,et al.  On the origin of the Azores Current , 1989 .

[34]  L. Talley,et al.  An eastern Atlantic section from Iceland southward across the equator , 1992 .

[35]  H. Rossby,et al.  Mediterranean Water: An Intense Mesoscale Eddy off the Bahamas , 1978, Science.

[36]  F. F. Pérèz,et al.  Vivaldi 1991 - A study of the formation, circulation and ventilation of Eastern North Atlantic Central Water , 1996 .

[37]  Robert C. Beardsley,et al.  Separation of Tidal and Subtidal Currents in Ship-Mounted Acoustic Doppler Current Profiler Observations , 1992 .

[38]  Gerd Krahmann,et al.  Formation and Propagation of Temperature Anomalies along the North Atlantic Current , 2001 .

[39]  M. Arhan,et al.  The Water Masses of the Central North Atlantic in 1983—84 , 1988 .

[40]  G. Flierl.  Rossby Wave Radiation from a Strongly Nonlinear Warm Eddy , 1984 .

[41]  P. Richardson,et al.  A census of Meddies tracked by floats , 2000 .

[42]  M. Arhan,et al.  The North Atlantic Current and Subarctic Intermediate Water , 1990 .

[43]  C. Adduce,et al.  An experimental study of a mesoscale vortex colliding with topography of varying geometry in a rotating fluid , 2004 .

[44]  K. Speer,et al.  Directly measured mid-depth circulation in the northeastern North Atlantic Ocean , 2002, Nature.

[45]  W. Dewar,et al.  Meddy–Seamount Interactions: Implications for the Mediterranean Salt Tongue , 2003 .

[46]  Steven Herbette,et al.  Erosion of a Surface Vortex by a Seamount , 2003 .

[47]  Y. Morel,et al.  Interaction between an eddy and a zonal jet , 2003 .